Apparatus for conveying printing sheets

ABSTRACT

A conveying apparatus for conveying sheets to a printing press includes at least one suction belt movable over a table; at least one suction chamber disposed below the table for sucking air through the at least one suction belt, so that the sheets are sucked on the at least one suction belt and guided along the table to the printing press; a pressure reducing means for reducing air pressure within said at least one suction chamber; and an air pressure controlling means for controlling said pressure reducing means according to the information regarding the sheets inputted to said air pressure controlling means, thereby adjusting the reduction in the air pressure within the at least one suction chamber.

BACKGROUD OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a conveying apparatus that includes a table for conveying printing sheets with a suction force applied thereon to a printing press.

[0003] 2. Discussion of the Background

[0004] Hitherto, for conveying printing paper or printing sheets to a printing press, a conveying apparatus equipped with a suction belt, which moves over a table as sucking the printing sheets has been used. The conveying apparatus of this type generally includes a table, at least one suction chamber disposed below the table, an axial flow fan connected with the at least one suction chamber and a suction belt that moves over the table as sucking the printing sheets.

[0005] For example, Japanese Patent No. 2531861 discloses a conveying apparatus for conveying printing sheets to a printing press by using a table of the above type.

[0006]FIG. 5 illustrates a schematic structural view of the conventional conveying apparatus. In conveying apparatus 50 as illustrated in this Figure, table 53 is disposed between printing press 21 and sheet feeding unit 22. Below the table 53 is disposed suction chamber 56 with its lower side connected with axial flow fan 55 driven by vacuum motor 54. Suction belt 58 with suction holes is guided on the table 53. The suction chamber 56 and the axial flow fan 55 together form a single, common chamber. The belt 58 travels around tensioning rollers 57, 62 on the underside of the table 53 and around driving shafts 59, 60 at the table ends. The table 53 is continuously perforated near the guide for the belt 58, thereby generating an airflow from the top of the table 53 by the suction chamber 56 and the axial flow fan 55 over the entire length of the table 53.

[0007] The sheets are conveyed from the sheet feeding unit 22 in overlapping form. That is, the sheets conveyed by the tables each have a rear end, as viewed in the sheet running direction, positioned above the front end of the immediately following sheet. The sheets on the table 53 are sucked by the suction belt to be securely held on the surface of the table and conveyed towards the printing press 21. The respective sheets released from the table 53 are subjected to registration along front edges and lateral edges at registration unit 63, and then transferred to the printing press 21.

[0008] Meanwhile, according to the conveying apparatus 50 having such a conventional arrangement, various measures are taken to securely convey printing sheets on the suction belt 58, which travels over the table 53, to the printing press 21, which include controlling the axial flow fan 55 driven by the vacuum motor 54, which is connected with an inverter controller or any other type of a controller, and controlling opening/closing amounts of openings 51, 52 in the suction chamber 56.

[0009] Accordingly, air pressure in the suction chamber 56 is adjusted by controlling the axial flow fan 55 or opening/closing amounts of the openings 51, 52 of the suction chamber 56, which must be done manually by an operator who controls rotation of the vacuum motor 54 for driving the axial flow fan 55 or opening/closing amounts of the openings 51, 52 in the suction chamber 56 based upon his or her experience, or the information of sheets to be conveyed, such as size, thickness, stiffness and type of each sheet. This manual operation therefore requires an experienced or skilled operator, so that where poor adjustment was made, a trouble in feeding the sheets may occur, which leads to occurrence of defective sheets and hence to deteriorated efficiency in operation of the printing press.

[0010] To address the above problem, it is an object of the present invention to provide a conveying apparatus that is capable of properly conveying printing sheets without requiring an operator to pay a great attention to the adjustment of air pressure in the suction chamber or without requiring a well experienced or skilled operator.

SUMMARY OF THE INVENTION

[0011] According to a first aspect of the present invention, there is provided a conveying apparatus for conveying sheets to a printing press that includes: at least one suction belt movable over a table; at least one suction chamber disposed below the table for sucking air through the at least one suction belt, so that the sheets are sucked on the at least one suction belt and guided along the table to the printing press; a pressure reducing means for reducing air pressure within the at least one suction chamber; and an air pressure controlling means for controlling the pressure reducing means according to the information regarding the sheets inputted to the air pressure controlling means, thereby adjusting the reduction in the air pressure within the at least one suction chamber.

[0012] With the conveying apparatus having the above arrangement, the sheets placed on the at least one suction belt, which moves over the table, are sucked on the at least one suction belt by the reduction of the air pressure within the suction chamber and conveyed, while the air pressure within the at least one suction chamber is adjusted to a proper level during the conveyance. That is, the air pressure controlling means controls the pressure reducing means according to the information regarding the sheets inputted to the air pressure controlling means, thereby adjusting the reduction in the air pressure within the at least one suction chamber through the opening means. As a result, even the operator with less experience can achieve a smooth operation without paying a great attention to an air pressure level within the at least one suction chamber, as well as achieving reducing disorder in a sheet feeding operation, minimizing occurrence of defective sheets, and hence preventing deteriorated efficiency in operation of the printing press.

[0013] According to another aspect of the present invention, there is provided a conveying apparatus for conveying sheets to a printing press that includes: at least one suction belt movable over a table; at least one suction chamber disposed below the table for sucking air through the at least one suction belt, so that the sheets are sucked on the at least one suction belt and guided along the table to the printing press; a pressure reducing means for reducing air pressure within the at least one suction chamber; and an air pressure controlling means for controlling the pressure reducing means according to an air pressure within the at least one suction chamber measured at the start of a sheet feeding operation, thereby adjusting the reduction in the air pressure within the at least one suction chamber.

[0014] With the conveying apparatus having the above arrangement, the sheets placed on the at least one suction belt, which moves over the table, are sucked on the at least one suction belt by the reduction of the air pressure within the suction chamber and conveyed, while the air pressure within the at least one suction chamber is adjusted to a proper level during the conveyance. That is, the air pressure controlling means controls the pressure reducing means according to the air pressure within the at least one suction chamber detected at the start of a sheet feeding operation, thereby adjusting the reduction in the air pressure within the at least one suction chamber through the opening means. As a result, even the operator with less experience can achieve a smooth operation without paying a great attention to an air pressure level within the at least one suction chamber, as well as achieving reducing disorder in a sheet feeding operation, minimizing occurrence of defective sheets, and hence preventing deteriorated efficiency in operation of the printing press.

[0015] According to another aspect of the present invention, there is provided a conveying apparatus for conveying sheets to a printing press that includes: at least one suction belt movable over a table; at least one suction chamber disposed below the table for sucking air through the at least one suction belt, so that the sheets are sucked on the at least one suction belt and guided along the table to the printing press; a pressure reducing means for reducing air pressure within the at least one suction chamber; and an air pressure controlling means for controlling an opening means for adjusting an opening/closing amount of an opening formed in each of the at least one suction chamber according to the information regarding the sheets inputted to the air pressure controlling means, thereby adjusting the reduction in the air pressure within the at least one suction chamber.

[0016] With the conveying apparatus having the above arrangement, the sheets placed on the at least one suction belt, which moves over the table, are sucked on the at least one suction belt by the reduction of the air pressure within the suction chamber and conveyed, while the air pressure within the at least one suction chamber is adjusted to a proper level during the conveyance. That is, the air pressure controlling means controls an opening means for adjusting an opening/closing amount of an opening formed in each of the at least one suction chamber according to the information regarding the sheets inputted to the air pressure controlling means, thereby adjusting the reduction in the air pressure within the at least one suction chamber through the pressure reducing means. As a result, even the operator with less experience can achieve a smooth operation without paying a great attention to an air pressure level within the at least one suction chamber, as well as achieving reducing disorder in a sheet feeding operation, minimizing occurrence of defective sheets, and hence preventing deteriorated efficiency in operation of the printing press.

[0017] According to yet another aspect of the present invention, there is provided a conveying apparatus for conveying sheets to a printing press that includes: at least one suction belt movable over a table; at least one suction chamber disposed below the table for sucking air through the at least one suction belt, so that the sheets are sucked on the at least one suction belt and guided along the table to the printing press; a pressure reducing means for reducing air pressure within the at least one suction chamber; and an air pressure controlling means for controlling an opening means for adjusting an opening/closing amount of an opening formed in each of the at least one suction chamber according to an air pressure within the at least one suction chamber measured at the start of a sheet feeding operation, thereby adjusting the reduction in the air pressure within the at least one suction chamber.

[0018] With the conveying apparatus having the above arrangement, the sheets placed on the at least one suction belt, which moves over the table, are sucked on the at least one suction belt by the reduction of the air pressure within the suction chamber and conveyed, while the air pressure within the at least one suction chamber is adjusted to a proper level during the conveyance. That is, the air pressure controlling means controls an opening means for adjusting an opening/closing amount of an opening formed in each of the at least one suction chamber according to the air pressure within the at least one suction chamber detected at the start of a sheet feeding operation, thereby adjusting the reduction in the air pressure within the at least one suction chamber through the pressure reducing means. As a result, even the operator with less experience can achieve a smooth operation without paying a great attention to an air pressure level within the at least one suction chamber, as well as achieving reducing disorder in a sheet feeding operation, minimizing occurrence of defective sheets, and hence preventing deteriorated efficiency in operation of the printing press.

[0019] The information inputted to the air pressure controlling means preferably includes at least one of size, thickness, stiffness and type of each of the sheets. With this information, the operator can achieve a sheet feeding operation without the necessity to manually adjust the air pressure within the at least one suction chamber, since the air pressure is properly adjusted according to the information including various parameters of the sheets, such as size, thickness, stiffness and type.

[0020] The adjustment of the reduction in the air pressure within the at least one suction chamber is preferably made according to the information obtained from the result of an operation test. By the operation according to the information obtained from the result of an operation test, there causes little variation in defect rate of the sheets fed due to variation in operator's experience, thereby achieving a stabilized sheet feeding operation without the necessity to manually adjust the air pressure by the operator.

[0021] The conveying apparatus according to any one of the aspects of the present invention preferably further comprises a sensor for detecting a state of the sheets conveyed along the table. With this sensor, the state of the sheets conveyed along the table can be detected, enabling proper and timely correction of the air pressure within the at least one suction chamber.

[0022] Alternatively, the conveying apparatus preferably further comprises a sensor for detecting the air pressure within the suction chamber. With this sensor, the air pressure within the at least one of the suction chamber can be detected, enabling proper and timely correction of the air pressure within the at least one suction chamber.

[0023] The air pressure controlling means preferably controls the pressure reducing means according to the output of any one of the above sensors. By this controlling, where the output of the sensor is varied, the air pressure controlling means automatically controls the pressure reducing means, thereby correcting the air pressure within the at least one suction chamber to a proper pressure level.

[0024] Alternatively, the air pressure controlling means preferably controls the opening means for adjusting an opening/closing amount of the opening formed in each of the at least one suction chamber according to the output of any one of the sensors. With this controlling, where such as the output of the sensor is varied, the air pressure controlling means automatically controls the opening means for adjusting an opening/closing amount of the opening formed in each of the at least one suction chamber, thereby correcting the air pressure within the at least one suction chamber to a proper pressure level.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above, and other objects, features and advantages of the present invention will become apparent from the detailed description thereof in conjunction with the accompanying drawings wherein.

[0026]FIG. 1 is a block diagram illustrating a controller provided in the conveying apparatus according to a first embodiment of the present invention.

[0027]FIG. 2 is a schematic structural view illustrating the conveying apparatus according to the first embodiment of the present invention.

[0028]FIG. 3 is a block diagram illustrating a controller provided in the conveying apparatus according to a second embodiment of the present invention.

[0029]FIG. 4 is a schematic structural view illustrating the conveying apparatus according to the second embodiment of the present invention.

[0030]FIG. 5 is a schematic structural view of the conventional conveying apparatus.

DETAILED DESCRIPTION OF THE PREFFERERED EMBODIMENT

[0031] Embodiments of the conveying apparatus according to the present invention will be hereinafter described with reference to the drawings as attached hereto.

[0032]FIG. 1 is a block diagram illustrating a controller provided in the conveying apparatus according to the first embodiment of the present invention. In this Figure, controller 10 includes operation panel 1 for inputting various information such as an operational condition for conveying sheets, microcomputer 2 for performing a predetermined process based upon the information inputted through the operation panel 1, vacuum-motor-drive-circuit 5 for inverter control of vacuum motor 6 as a pressure reducing means (vacuum motors 27, 29 in FIG. 2), sensors 3 disposed in suction chambers 24, 25 along a sheet conveying line on table 23 (see FIG. 2, in which pressure sensors 41, 42 and line sensors 39, 40 respectively correspond thereto), encoder 4 for synchronizing the traveling speed of suction belts 30, 31 (FIG. 2) with the printing speed of a printing press, and drive circuit 7 for driving conveying motor 8, which drives the suction belts 30, 31. The microcomputer 2 includes information storage means 2 a for storing various information on, for example, parameters of printing sheet 8, control programs, etc., and air pressure control means 2 b for adjusting pressure reduction of the air in the suction chambers 24, 25 by controlling the vacuum motor 6 (vacuum motors 27, 29 in FIG. 2) or correcting the rotation of the same through the vacuum-motor-drive-circuit 5 based upon the information regarding printing sheets or control programs stored in the information storage means 2 a.

[0033]FIG. 2 is a schematic structural view of the conveying apparatus according to the first embodiment of the present invention. In the conveying apparatus 20 of this Figure, the suction chambers 24, 25 are disposed below the table 23, aligned along a sheet conveying path, and respectively provided in their inside spaces with the pressure sensors 41, 42 for detecting the air pressures. The suction chambers 24, 25 are respectively connected with axial flow fans 26, 28, which are in turn respectively equipped with the vacuum motors 27, 29 so as to be capable of being respectively and independently controlled. The suction belt 30, which is guided by drive shafts 32, 34, guide shaft 33 and tensioning rollers 35, 36, circulates around the suction chamber 24.

[0034] The table 23 forms over its entire length suction orifices (not shown), through which air is sucked. Additional suction belt 31 is guided around the suction chamber 25 by the drive shaft 34, the guide shaft 33 and the tensioning rollers 37, 38 to form a sheet transferring section between the table 23 and the printing press 21. The line sensors 39, 40 or any other sensing means for detecting a state of the sheets conveyed on the table 23 are disposed at predetermined positions along the sheet conveying path on the table 23.

[0035] Now, the description will be made for the operation of the apparatus according to this embodiment with reference to FIGS. 1 and 2. The information storage means 2 a of the microcomputer 2 stores the information such as various parameters of the printing sheets including size, thickness, stiffness and type, as well as a control program for controlling the drive of the vacuum motors 27, 29 based upon the information stored in the information storage means 2 a.

[0036] For printing on sheets, the information regarding the size, thickness, stiffness, type and/or the like of the sheets are inputted into the microcomputer 2 by operating the operation panel 1. Then, the conveying apparatus 20 is activated by operating a start switch on the operation panel 1, thereby enabling the suction belts 30, 31 to travel over the table 23, and the axial flow fans 26, 28 to be activated by the rotation of the vacuum motor unit 6 (vacuum motors 27, 29), thereby reducing air pressures in the suction chambers 24, 25.

[0037] The air pressure control means 2 b of the microcomputer 2 transmits control signals for controlling the vacuum motors 27, 29 based upon the parameters of the sheets inputted through the operation panel 1 to the vacuum-motor-drive-circuit 5. By controlling this vacuum-motor-drive-circuit 5, the rotation number of the vacuum motor 6 (vacuum motors 27, 29) is varied. Thus, the air pressures in the suction chambers 24, 25 are varied according to the rotation numbers of the vacuum motor 6. With this arrangement, the sheets discharged from the sheet feeding unit 22 are placed on the suction belts 30, 31 on the table 23, and then guided to the printing press 21 with their undersides sucked against the table 23.

[0038] At least during travel of the sheets placed on the suction belts 30, 31 over the length of the table 23, the air pressures in the suction chambers 24, 25 are monitored by the pressure sensors 41, 42, while a state of the sheets during their conveyance is also monitored by the line sensors 39, 40, so that the air pressure control means 2 b of the microcomputer 2 controls the vacuum-motor-drive-circuit 5 based upon the respective outputs of the pressure sensors 41, 42 and outputs of the line sensors 39, 40, thereby setting the rotation number of the vacuum motor 6 (vacuum motors 27, 29) at a predetermined number. Whereby, suction forces of the suction belts 30, 31 on the table 23 are properly set according to the size, thickness, stiffness and/or type of sheets, conveying speed, or any other conditions such as air flow or air blow relating to the operation of the apparatus.

[0039]FIG. 3 is a block diagram illustrating the arrangement of the controller provided in the conveying apparatus according to the second embodiment of the present invention. FIG. 4 is a schematic structural view of the conveying apparatus according to the second embodiment of the present invention, in which corresponding or identical parts to those of the first embodiment have been given the same reference characters with primes (′).

[0040] Controller 12 as illustrated in FIG. 3 includes operation panel 1′ for inputting various information such as operation condition for conveying sheets, microcomputer 2′ for performing a predetermined process based upon the information inputted through the operation panel 1′, control circuit 9 for controlling opening adjustment means 11 for adjusting opening/closing amounts of opening 45, 46, 47, 48 formed in suction chambers 24′, 25′ so as to adjust the suction rates of air into the suction chambers, sensors 3′ disposed in the suction chambers 24′, 25′ and along the sheet conveying line on table 23′ (see FIG. 4, in which pressure sensors 41′, 42′ and line sensors 39′, 40′ respectively correspond thereto), encoder 4′ for synchronizing the traveling speed of suction belts 30′, 31′ (FIG. 4) with the printing speed of a printing press 21′, and drive circuit 7′ for driving conveying motor 8′, which drives the suction belts 30′, 31′. The microcomputer 2′ includes information storage means 2 a′ for storing various information on, for example, parameters of printing sheets, control programs, etc., and air pressure control means 2 b′ for adjusting air pressure in the suction chambers 24′, 25′ by controlling the opening adjustment means 11 for adjusting opening/closing amounts of the openings 45, 46, 47, 48 formed in the suction chambers 24′, 25′. Specifically, the opening adjustment means 11 is herein embodied as opening/closing amount varying mechanisms (not shown) that are capable of adjusting the opening/closing amounts of the openings 45, 46, 47, 48 based upon electrical signals transmitted from the control circuit 9. More specifically, the opening/closing amount varying mechanism may include two slider plates, which respectively have openings and are stacked to each other. One of the slider plates is fixed in position and the other is slidable over the opposite slider plate, so that the opening/closing amounts of the openings 45, 46, 47, 48 are varied according to an overlapping amount between two slider plates, resembling an aperture mechanism of a camera using shutter blades. That is, the openings 45, 46, 47, 48 are fully opened when those plates are in a completely overlapped state, while they are fully closed when those plates are out of the overlapped state.

[0041] In conveying apparatus 70 of FIG. 4, the table 23′ is provided with the two suction chambers 24′, 25′, which are aligned along the sheet conveying path and respectively provided in their inside spaces with the pressure sensors 41′, 42′ for detecting the air pressures. The suction chambers 24′, 25′ respectively form in their upper sides the openings 45, 46, and the openings 47, 48. The suction chambers 24′, 25′ are connected with axial flow fans 26′, 28′, which are in turn respectively equipped with vacuum motors 27′, 29′ so as to be capable of being respectively and independently controlled. The suction belt 30′, which is guided by drive shafts 32′, 34′, guide shaft 33′ and tensioning rollers 35′, 36′ circulates around the suction chamber 24′.

[0042] The table 23′ forms over its entire length suction orifices (not shown), through which air is sucked. Additional suction belt 31′ is guided around the suction chamber 25′ by the drive shaft 34′, the guide shaft 33′ and the tensioning rollers 37′, 38′ to form a sheet transferring section between the table 23′ and the printing press 21′. The line sensors 39′, 40′ or any other sensing means for detecting a state of the sheets conveyed on the table 23′ are disposed at predetermined positions along the sheet conveying path on the table 23′.

[0043] Now, the description will be made for the operation of the apparatus according to this embodiment with reference to FIGS. 3 and 4. The information storage means 2 a′ of the microcomputer 2′ stores the information such as various parameters of the printing sheets including size, thickness, stiffness and type, as well as a control program for controlling the opening adjustment means 11 for adjusting the opening/closing amounts of the openings 45, 46, 47, 48 based upon the information stored in the information storage means 2 a′.

[0044] For printing on sheets, the information regarding the size, thickness, stiffness, type and/or the like of the sheets are inputted into the microcomputer 2′ by operating the operation panel 1′. Then, the conveying apparatus 70 is activated by operating a start switch on the operation panel 1′, thereby enabling the suction belts 30′, 31′ to travel over the table 23′, and the axial flow fans 26′, 28′ to be activated by the rotation of the vacuum motors 27′, 29′, thereby reducing air pressures in the suction chambers 24′, 25′.

[0045] The air pressure control means 2 b′ of the microcomputer 2′ transmits control signals for controlling the opening adjustment means 11 for adjusting the opening/closing amounts of the openings 45, 46, 47, 48 based upon the sheet information inputted through the operation panel 1′ to the control circuit 9. By controlling this control circuit 9, the opening/closing amounts of the openings 45, 46, 47, 48 are varied through the opening adjustment means 11. Thus, the air pressures in the suction chambers 24′, 25′ are varied according to the opening/closing amounts of the openings 45, 46, 47, 48. With this arrangement, the sheets discharged from the sheet feeding unit 22′ are placed on the suction belts 30′, 31′ on the table 23′, and then guided to the printing press 21′ with their undersides sucked against the table 23′.

[0046] At least during travel of the sheets placed on the suction belts 30′, 31′ over the length of the table 23′, the air pressures in the suction chambers 24′, 25′ are monitored by the pressure sensors 41′, 42′, while a state of the sheets during their conveyance is also monitored by the line sensors 39′, 40′, so that the air pressure control means 2 b′ of the microcomputer 2′ controls the opening adjustment means 11 for properly adjusting the opening/closing amounts of the openings 45, 46, 47, 48 via the control circuit 9 based upon the respective outputs of the pressure sensors 41′, 42′ and outputs of the line sensors 39′, 40′, thereby varying the air pressures within the suction chambers 24′, 25′. Whereby, suction forces of the suction belts 30′, 31′ on the table 23′ are properly set according to the size, thickness, stiffness and/or type of sheets, conveying speed, or any other conditions such as air flow or air blow relating to the operation of the apparatus.

[0047] In the aforesaid embodiments, both the pressure sensors and line sensors are provided respectively for detecting the air pressures in the suction chambers and the sheet conveying state. However, the present invention is not necessarily limited to this arrangement. Accordingly, either one of the pressure sensors and line sensors may provided, while accuracy in adjusting the air pressures in the suction chambers can be increased by providing both pressure and line sensors.

[0048] In the above embodiments, the air pressures within the suction chambers are adjusted based upon the inputted information regarding sheets to be printed. This is not essential for the present invention. Rather, the adjustment of the air pressures within the suction chambers may be made based upon the air pressures in the suction chambers detected at the start of a sheet feeding operation.

[0049] That is, the air pressures within the suction chambers are varied before and after the start of the sheet feeding operation due to the presence and absence of the sheets on the suction belts. To first find proper air pressure levels within the suction chambers, which contribute to most smooth sheet conveyance for each of size, thickness, stiffness, and types, air pressures within the suction chambers are varied during the conveyance of sheets of varying size, thickness, stiffness and type. Then, by varying the air pressures within the suction chambers before the start of the sheet feeding operation, air pressures that come to the aforesaid proper air pressures after the start of the sheet feeding operation are determined.

[0050] Data representative of those air pressure levels that come to the proper air pressures as described above are stored in a storage means of the microcomputer. The conveying apparatus is then activated with the pressure sensors detecting the air pressure levels in the suction chambers at the start of the sheet feeding operation. Then, the air pressure control means of the microcomputer reads out the data from the storage means, and adjusts air pressure detected by the pressure sensors to the proper pressure levels at the start of the sheet feeding operation. Thus, the sheets of varying size, thickness, stiffness and type can be smoothly conveyed along the table with the proper air pressures without adjusting the air pressures during the sheet conveyance.

[0051] The adjustment of air pressure reduction in the suction chambers may be made according to data representative of various information, which are previously collected by conducting an operation test, stored in the storage means of the microcomputer, and read out therefrom with or without reference to the initial pressure levels.

[0052] In the above embodiments, the controller of the conveying apparatus is designed to control two suction chambers. This is not essential for the present invention. Rather, the controller can control the conveying apparatus with a single chamber in the same manner as the above.

[0053] This specification is by no means intended to restrict the present invention to the preferred embodiments set forth therein. Various modifications to the conveying apparatus, as described herein, may be made by those skilled in the art without departing from the spirit and scope of the present invention as defined in the appended claims. 

What is claimed is:
 1. A conveying apparatus for conveying sheets to a printing press comprising: at least one suction belt movable over a table; at least one suction chamber disposed below the table for sucking air through the at least one suction belt, so that the sheets are sucked on the at least one suction belt and guided along the table to the printing press; a pressure reducing means for reducing air pressure within said at least one suction chamber; and an air pressure controlling means for controlling said pressure reducing means according to the information regarding the sheets inputted to said air pressure controlling means, thereby adjusting the reduction in the air pressure within the at least one suction chamber.
 2. A conveying apparatus for conveying sheets to a printing press comprising: at least one suction belt movable over a table; at least one suction chamber disposed below the table for sucking air through the at least one suction belt, so that the sheets are sucked on the at least one suction belt and guided along the table to the printing press; a pressure reducing means for reducing air pressure within said at least one suction chamber; and an air pressure controlling means for controlling said pressure reducing means according to an air pressure within the at least one suction chamber measured at the start of a sheet feeding operation, thereby adjusting the reduction in said air pressure within the at least one suction chamber.
 3. A conveying apparatus for conveying sheets to a printing press comprising: at least one suction belt movable over a table; at least one suction chamber disposed below the table for sucking air through the at least one suction belt, so that the sheets are sucked on the at least one suction belt and guided along the table to the printing press; a pressure reducing means for reducing air pressure within said at least one suction chamber; and an air pressure controlling means for controlling an opening means for adjusting an opening/closing amount of an opening formed in each of the at least one suction chamber according to the information regarding the sheets inputted to said air pressure controlling means, thereby adjusting the reduction in said air pressure within the at least one suction chamber.
 4. A conveying apparatus for conveying sheets to a printing press comprising: at least one suction belt movable over a table; at least one suction chamber disposed below the table for sucking air through the at least one suction belt, so that the sheets are sucked on the at least one suction belt and guided along the table to the printing press; a pressure reducing means for reducing air pressure within said at least one suction chamber; and an air pressure controlling means for controlling an opening means for adjusting an opening/closing amount of an opening formed in each of the at least one suction chamber according to an air pressure within the at least one suction chamber measured at the start of a sheet feeding operation, thereby adjusting the reduction in said air pressure within the at least one suction chamber.
 5. A conveying apparatus according to claim 1, wherein the information inputted to the air pressure controlling means includes at least one of size, thickness, stiffness and type of each of the sheets.
 6. A conveying apparatus according to claim 3, wherein the information inputted to the air pressure controlling means includes at least one of size, thickness, stiffness and type of each of the sheets.
 7. A conveying apparatus according to claim 1, wherein the adjustment of the reduction in the air pressure within the at least one suction chamber is made according to the information obtained from the result of an operation test.
 8. A conveying apparatus according to claim 2, wherein the adjustment of the reduction in the air pressure within the at least one suction chamber is made according to the information obtained from the result of an operation test.
 9. A conveying apparatus according to claim 3, wherein the adjustment of the reduction in the air pressure within the at least one suction chamber is made according to the information obtained from the result of an operation test.
 10. A conveying apparatus according to claim 4, wherein the adjustment of the reduction in the air pressure within the at least one suction chamber is made according to the information obtained from the result of an operation test.
 11. A conveying apparatus according to claim 1, which further comprises a sensor for detecting a state of the sheets conveyed along the table.
 12. A conveying apparatus according to claim 2, which further comprises a sensor for detecting a state of the sheets conveyed along the table.
 13. A conveying apparatus according to claim 3, which further comprises a sensor for detecting a state of the sheets conveyed along the table.
 14. A conveying apparatus according to claim 4, which further comprises a sensor for detecting a state of the sheets conveyed along the table.
 15. A conveying apparatus according to claim 1, which further comprises a sensor for detecting the air pressure within the suction chamber.
 16. A conveying apparatus according to claim 2, which further comprises a sensor for detecting the air pressure within the suction chamber.
 17. A conveying apparatus according to claim 3, which further comprises a sensor for detecting the air pressure within the suction chamber.
 18. A conveying apparatus according to claim 4, which further comprises a sensor for detecting the air pressure within the suction chamber.
 19. A conveying apparatus according to claim 1, which further comprises a sensor for detecting a state of the sheet conveyed along the table, in which the air pressure controlling means controls the pressure reducing means according to the output of said sensor.
 20. A conveying apparatus according to claim 2, which further comprises a sensor for detecting a state of the sheet conveyed along the table, in which the air pressure controlling means controls the pressure reducing means according to the output of said sensor.
 21. A conveying apparatus according to claim 1, which further comprises a sensor for detecting an air pressure within the at least one suction chamber, in which the air pressure controlling means controls the pressure reducing means according to the output of said sensor.
 22. A conveying apparatus according to claim 2, which further comprises a sensor for detecting an air pressure within the at least one suction chamber, in which the air pressure controlling means controls the pressure reducing means according to the output of said sensor.
 23. A conveying apparatus according to claim 3, which further comprises a sensor for detecting a state of the sheet conveyed along the table, in which the air pressure controlling means controls the opening means for adjusting an opening/closing amount of the opening formed in each of the at least one suction chamber according to the output of said sensor.
 24. A conveying apparatus according to claim 4, which further comprises a sensor for detecting a state of the sheet conveyed along the table, in which the air pressure controlling means controls the opening means for adjusting an opening/closing amount of the opening formed in each of the at least one suction chamber according to the output of said sensor.
 25. A conveying apparatus according to claim 3, which further comprises a sensor for detecting an air pressure within the at least one suction chamber, in which the air pressure controlling means controls the opening means for adjusting an opening/closing amount of the opening formed in each of the at least one suction chamber according to the output of said sensor.
 26. A conveying apparatus according to claim 4, which further comprises a sensor for detecting an air pressure within the at least one suction chamber, in which the air pressure controlling means controls the opening means for adjusting an opening/closing amount of the opening formed in each of the at least one suction chamber according to the output of said sensor. 